Recent evidence from our group and others has suggested that exposure to polychlorinated biphenyls (PCBs) can cause metabolic oxidative stress in mammalian cells contributing to cell injury and the biological effects of PCBs. Chronic metabolic oxidative stress has also been strongly implicated in degenerative diseases associated with genomic instability, carcinogenesis, and aging.PCB exposure has also been implicated in increased the risk of prostate and breast cancer. Project 2 will investigate the involvement of metabolic oxidative stress in mechanisms of injury and growth disturbances seen in human prostate and breast epithelial cells during PCB exposure. Preliminary results show that exposure of prostate epithelial cells (PrECB) and breast epithelial cells (MCF10A) to PCBs and PCB metabolites cause increased superoxide production and disruptions in glutathione metabolism consistent with induction of metabolic oxidative stress as well as perturbations in cell growth. Specifically the current proposal will test the hypothesis that mitochondria! production of reactive oxygen species (ROS;i.e., superoxide and hydrogen peroxide) causes oxidative stress during PCB exposure and this increased production of ROS contributes to the biological effects of PCBs on cell growth in prostate and breast epithelial cells. Aim#1 will determine if exposure to PCBs or PCB metabolites induces oxidative stress in prostate and breast epithelial cells that contributes to PCB-induced alterations in cell proliferation and cytotoxicity. Aim#2 will determine which specific ROS (i.e., superoxide, hydrogen peroxide, and organic hydroperoxides) and sites of production contribute to oxidative stress and PCB-induced growth disturbances and cytotoxicity in prostate and breast epithelial cells. Aim#3 will determine if manipulation of intracellular thiols or selenium supplementation can modify PCB-induced oxidative stress and growth disturbances in human prostate and breast epithelial cells. The long-term goal of these studies is to provide a rigorous mechanistic understanding of the involvement of metabolic oxidative stress in PCB-induced effects on prostate and breast epithelial cell growth that may contribute carcinogenesis and identify manipulations of antioxidant mechanisms that can protect human prostate and breast epithelial cells from PCB exposure.